1. Field
The following description relates to multicast service technology, and more particularly, to an apparatus and method for transmitting multi-carriers to provide a high-quality service to service subscriber terminals.
2. Description of the Related Art
A Multicast Broadcast Service (MBS) zone is composed of several base stations, wherein all the base stations transmit multicast data simultaneously using the same radio resources in time and frequency domains. Accordingly, terminals located near the borders of neighboring cells can obtain macro diversity gain for MBS.
A multicast service enables terminals to receive the same service through the same radio resources. However, since terminals have different wireless channel conditions, a scheduler of each base station has to perform scheduling suitable for a terminal having the worst channel condition among all terminals that requested to receive the multicast service, in order to provide the multicast service to all the terminals. That is, the multicast service could not distinguish terminals having good channel conditions from ones having poor channel conditions.
Also, there is a service based on scheduling of setting a threshold channel condition, classifying terminals that requested to receive a multicast service into two or more groups according to the threshold channel condition, and allocating different radio resources to the groups, respectively.
However, both the methods described above caused a waste of resources. That is, since the former performs scheduling based on a terminal having the worst channel condition, a low code rate has to be applied to terminals having good channel conditions, and signals from the terminals having good channel conditions also have to be transmitted with a high power intensity. Meanwhile, since the latter overlappingly allocates radio resources to different groups, a waste of radio resources is caused.
Multi-carrier resource allocation technology using two or more radio frequencies (RF) can allocate a plurality of radio frequencies to each terminal. However, if carriers are equally allocated to all terminals that use a multicast service, regardless of their channel conditions, the multicast service cannot provide the effect of throughput improvement which is the use purpose of multi-carrier.